As elements, resistors, inductors and capacitors are generally used. Though each of these elements is manufactured individually, it is difficult to manufacture pure elements. Capacitors, for example, have some leakage resistance, and resistors include some capacitance and inductance. In most cases, each of the three kinds of elements includes impurities of the two other units.
A.C. bridge method is usually applied to make precise measurement of value of the element including impure components. However, in order to balance the bridge circuit, for instance, the voltage across the standard component or the standard itself must be adjusted. Additionally, to minimize or compensate phase difference caused by the variable voltage source or the variable standard, expensive circuit parts or complicated circuit composition are needed. As a result, the conventional instrument is expensive and lacks reliability in spite of taking more time for adjustment.